The present invention relates to compounds that are useful, inter alia, as catalysts or catalyst components. More particularly, the present invention relates to dicationic compounds comprising a Group 4 metal atom (Ti, Zr, Hf) that are particularly adapted for use in the coordination polymerization of unsaturated compounds. Such compounds are particularly advantageous for use in a polymerization process wherein at least one polymerizable monomer is combined under polymerization conditions with a catalyst or catalyst composition to form a polymeric product.
It is previously known in the art to activate Ziegler-Natta polymerization catalysts, particularly such catalysts comprising Group 3-10 metal complexes containing delocalized xcfx80-bonded ligand groups, using Lewis acids to form catalytically active derivatives of such Group 3-10 metal complexes. Examples of suitable Lewis acids include tris(perfluorophenyl)borane and tris(perfluorobiphenyl)borane. Examples of such processes are disclosed in U.S. Pat. No. 5,721,185 and J. Am. Chem. Soc., 118, 12451-12452 (1996), and elsewhere.
According to J. Chem. Soc. Chem. Commun., 1999, 115-116, certain specifically substituted bis-Cp zirconocenedimethyl complexes may be converted to a dicationic derivative at xe2x88x9260xc2x0 C. using multiple equivalents of trispentafluorophenylborane. The resulting metallocenes required the presence of either pendant phosphine moieties or benzyl groups on the cyclopentadienyl ring system and two equivalents of the methyltris(pentafluorophenyl)borate anion for charge balance. Upon heating even to xe2x88x9240xc2x0 C. the product decomposed to give the corresponding monocationic complex and free tris(pentafluorophenyl)borane, thereby indicating the complexes would be unsuited for use as polymerization catalyst components.
In U.S. Pat. No. 5,318,935 metal complexes containing two amido groups optionally linked by means of a bridging group are disclosed.
Finally, in Orpanometallics, 1998, 17, 5908-5912, the reaction of the strongly Lewis acidic compound, tris(pentafluorophenyl)aluminum, with bis(cyclopentadienyl)zirconium dimethyl was shown to form an unstable (xcexc-methyl) derivative via methide abstraction, which rapidly collapsed through a back exchange reaction at temperatures above 0xc2x0 C. to form bis(cyclopentadienyl)methylpentafluoro-phenyl zirconium. These compounds also would find little use as catalyst components for addition polymerizations due to the lack of temperature stability.
All of the foregoing attempts have failed to prepare a metal complex that is useful in catalytic applications, especially in the polymerization of one or more ethylenically unsaturated monomers under addition polymerization conditions.
According to the present invention there are now provided dicationic Group 4 metal compounds corresponding to the formula: 
wherein:
Y1 and Y2 independently each occurrence is an anionic ligand group that is covalently bonded to M by means of a sigma bond through an oxygen, phosphorus or nitrogen atom, and containing up to 50 atoms, not counting hydrogen, said Y1 and Y2 optionally being joined through bridging group, J, and further optionally, Y1 and Y2 may also contain a coordinate/covalent bound to M;
J is an optional divalent bridging group having up to 20 atoms not counting hydrogen;
j is 0 or 1;
M is a Group 4 metal;
X1 independently each occurrence is a Lewis base;
x1 is 0, 1 or 2; and
Axe2x88x92 independently each occurrence is an anion of up to 50 atoms other than hydrogen, derived or derivable from a Lewis acid, said Axe2x88x92 optionally forming an adduct with the metal complex by means of a xcexcbridging group, and further optionally two Axe2x88x92 groups may be joined together thereby forming a single dianion, optionally containing one or more xcexc-bridging groups.
The compounds of the invention may be formed by contacting a charge-neutral Group 4 metal coordination complex having two monovalent, anionic ligand groups, X (or optionally the two X groups together form a single divalent, anionic ligand group), or precursor(s) thereof (catalyst) with at least 2 molar equivalents of a charge-neutral, Lewis acid compound (activator), A, or a mixture thereof, such that the X groups of the Group 4 metal coordination complex are abstracted or partially abstracted, thereby forming a charge separated cation/anion pair, a zwitterionic metal complex, or a complex having both cation/anion and zwitteron functionality. Preferably the molar ratio of catalyst:activator employed in the foregoing process is from 1:2 to 1:10, more preferably the ratio is from 1:2 to 1:3, and most preferably from 1:2 to 1:2.5.
The foregoing process is illustrated by the following schematic drawing: 
wherein
Y1, Y2, M, J, j, X, X1, x1, A, and Axe2x88x92, are as previously defined.
The present invented compounds are stable at elevated temperatures of at least 0xc2x0 C., preferably at least 20xc2x0 C. up to as high as 150xc2x0 C. or higher and are usefully employed in a process for polymerization of ethylenically unsaturated monomers under solution, slurry, high pressure, or gas phase polymerization conditions. Relatively high molecular weight polymers may be readily obtained by use of the present metal complexes in the foregoing polymerization processes. Additionally, the foregoing metal complexes are suitably employed as initiators or catalysts for cationic polymerizations, such as the cationic polymerization of styrene or isobutylene, ring opening polymerizations, such as the polymerization of oxiranes or epoxides, especially propylene oxide, and the copolymerization of an olefin, especially ethylene, with a ring openable monomer.
Accordingly, the present invention additionally provides a process for the polymerization of one or more ethylenically unsaturated, addition polymerizable monomers comprising contacting the same, optionally in the presence of an inert aliphatic, alicyclic or aromatic hydrocarbon, under polymerization conditions with the above metal complex, or alternatively, forming the above metal complex in situ in the presence of or prior to addition to, a reaction mixture comprising one or more ethylenically unsaturated, polymerizable compounds.
All references herein to elements belonging to a certain Group refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 1995. Also any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups. Where any reference is made herein to any publication, patent application or provisional patent application, the contents thereof are incorporated herein in its entirety by reference. By the term xe2x80x9cLewis acidxe2x80x9d, in reference to activator compounds herein, is meant compounds that are sufficiently electrophilic, such that a fully charge separated cation/anion pair, a xcexc-bridged complex or a zwiterionic complex is formed upon combination of the respective catalyst and activators. Preferred anionic ligand groups, X, are hydrocarbyl, silyl, N,N-dialkylamido and alkanediylamido groups of up to 20 atoms not counting hydrogen, or two such X groups together are an alkanediyl or alkenediyl group which together with M form a metallocycloalkane or metallocycloalkene. By the term xe2x80x9cpartially dicationicxe2x80x9d is meant that at least one Axe2x88x92 group (or the entity formed from two Axe2x88x92 groups collectively) is not fully charge separated from the metal center, M, or that at least one Axe2x88x92 group (or the entity formed from two Axe2x88x92 groups collectively) form a zwitterionic complex.
Preferred activators, A, are aluminum compounds containing at least one halohydrocarbyl ligand, preferably a fluoroaryl ligand. More preferred are tri(halohydrocarbyl)aluminum compounds having up to 50 atoms other than hydrogen, especially tri(fluoroaryl) aluminum compounds, most preferably tris(perfluoroaryl)aluminum compounds, and most highly preferably tris(pentafluorophenyl)aluminum. The activator compound may be used in pure form or in the form of an adduct with a Lewis base such as an ether.
Suitable Lewis acidic activators may be prepared by exchange between tris(pentafluorophenyl)boron and alkylaluminum- or alkyaluminumoxy- compounds such as alumoxanes or diisobutyl(2,6-di-t-butyl-4-methylphenoxy)aluminum, as disclosed in Biagini et. al., U.S. Pat. No. 5,602,269, and pending application U.S. Ser. No. 09/330673 (WO00/09515). The aluminum containing Lewis acids may be previously prepared and used in a relatively pure state or generated in situ by any of the foregoing techniques in the presence of the metal complex. Tris(perfluoroaryl)aluminum and exchange products obtained by mixing tris(perfluoroaryl)borane compounds, especially tris(pentafluoro-phenyl)boron, with methylalumoxane (MAO) or trialkylaluminum-, especially, triisobutylaluminum- modified methylalumoxane (MMAO) are highly preferred. This reaction product of tris(perfluoroaryl)boron with an alumoxane comprises a tris(fluoraryl)aluminum component of high Lewis acidity and a form of alumoxane which is rendered more Lewis acidic by the inherent removal of trimethylaluminum (TMA) via exchange to form trimethylborane. Optimized reaction products of these reactions correspond to the empirical formula:
(AlArf3xe2x88x92wxe2x80x2Q1wxe2x80x2)w(AlArf3xe2x88x92xxe2x80x2(OQ2)xxe2x80x2)x(AlQ13xe2x88x92yxe2x80x2(OQ2)yxe2x80x2)y[(xe2x80x94AlQ2xe2x80x94Oxe2x80x94)zxe2x80x2]z,
where;
Arf is a fluorinated aromatic hydrocarbyl moiety of from 6 to 30 carbon atoms; preferably fluoroaryl, more preferably perfluoroaryl, and most preferably pentafluorophenyl;
Q1 is C1-20 alkyl, preferably methyl;
Q2 is C1-20 hydrocarbyl, optionally substituted with one or more groups which independently each occurrence are hydrocarbyloxy, hydrocarbylsiloxy, hydrocarbylsilylamino, di(hydrocarbylsilyl)amino, hydrocarbylamino, di(hydrocarbyl)amino, di(hydrocarbyl)phosphino, or hydrocarbylsulfido groups having from 1 to 20 atoms other than hydrogen, or, optionally, two or more Q2 groups may be covalently linked with each other to form one or more fused rings or ring systems;
wxe2x80x2 is a number from 0 to 3;
w is a number from 0 to 1.0; preferably from 0.5 to 1.0, more preferably from 0.8 to 1.0;
xxe2x80x2 is a number from 0 to 3;
x is a number from 1.0 to 0; preferably from 0.5 to 0, more preferably from 0.2 to 0;
yxe2x80x2 is a number from 0 to 3;
y is a number from 1.0 to 0; preferably from 0.5 to 0, more preferably from 0.2 to 0;
zxe2x80x2 is a number from 0 to 30; and
z is a number from 0 to 20, preferably from 0 to 5, more preferably from 0 to 0.5.
The moieties, (AlArf3xe2x88x92wxe2x80x2Q1wxe2x80x2),(AlArf3xe2x88x92xxe2x80x2(OQ2)xxe2x80x2),AlQ13xe2x88x92yxe2x80x2(OQ2)yxe2x80x2), and [(xe2x80x94AlQ2xe2x80x94Oxe2x80x94)zxe2x80x2], may exist as discrete entities or as dynamic exchange products. That is, the foregoing formula is an idealized representation of the composition, which may actually exist in equilibrium with additional exchange products.
An additional suitable Lewis acid activator may be formed in situ by reaction of residual or excess Lewis acid activator, preferably, tris(pentaflurophenyl)aluminum, with the anion resulting from initial abstraction of an X group from the metal complex. Accordingly, such anions resulting from the foregoing reaction are of the formula: [Axe2x80x94xcexcXxe2x80x94A]xe2x88x92, where, Axe2x88x92 is the monovalent ligand derivative of A, preferably xe2x80x94Al(C6F5)3, and xcexcX is the xcexc-bridged derivative of X, preferably a xcexc-methyl group. An example of such an anion is [(C6F5)3Al-xcexc-CH3xe2x80x94Al(C6F5)3]xe2x88x92. However, because the group 4 metal complex and originally formed anion form a rather stable coordination pair under normal reaction conditions, the formation of the foregoing xcexc-methyl bridged anion is likely observed only under reaction conditions that would favor destabilization of the previously disclosed coordination pair.
Additional examples of the anion Axe2x88x92 are ligands of the formula: [M1Q4]xe2x88x92, where M1 is a Group 13 metal or metalloid, preferably Al, and Q independently each occurrence is an anionic ligand group, preferably an alkyl, aryl, aralkyl, or fluorinated aromatic ligand, that optionally may form a xcexc-bridge to the metal, M. Most preferred examples of this type of Axe2x88x92 anion are is [CH3Al(C6F5)3]xe2x88x92 and [xcexc-CH3Al(C6F5)3]xe2x88x92.
Exemplary J groups include O, as well as groups corresponding to the formula:
(ER*2)e, (BNR*2)e, or PR*2BR62,
wherein,
E independently each occurrence is C, Si, Sn, or Ge;
e=1,2,3, or 4;
R* independently each occurrence is C1-10 hydrocarbyl, or optionally two R* groups are joined together; and
R6 independently each occurrence is halide, or C1-12 hydrocarbyl.
Suitably, Y1 and Y2 are an amido group or phosphido group that is sigma bonded to M of the formula xe2x95x90NR1, or xe2x95x90PR1, where R1 is hydrocarbyl, dihydrocarbylaminohydrocarbyl, silyl, silylhydrocarbyl, hydrocarbylsilyl, or a cyclic or polycyclic, nitrogen containing ring system having up to 20 atoms, not counting hydrogen, and optionally R1 may be covalently or coordinately covalently bonded to J or M. Preferred sigma bonded ligand groups of the formulaxe2x95x90NR1 orxe2x95x90PR1, are those wherein R1 is alkyl or cycloalkyl of up to 10 carbons. Such complexes together with J form divalent bridging structures attached to the metal M.
Suitable compounds according to the present invention include compounds having the following structures: 
where M, R1, and Axe2x88x92 are as previously defined, and
R2, independently each occurrence is H or a hydrocarbyl, silyl, or trihydrocarbylsilyl-substituted hydrocarbyl group, said group having up to 20 atoms not counting hydrogen.
In the compounds of the invention, some or all of the bonds between M, Y1 and Y2 may possess partial bond characteristics. In addition, when Y1 or Y2 is a nitrogen containing, sigma bonded group, particularly a group of the formula,xe2x95x90NR1, when R1 is a primary alkyl group, an electronic interaction between the nitrogen and either one or both of the anionic moieties, Axe2x88x92, may occur.
The process for preparing the dicationic complexes of the invention is conducted at temperatures from xe2x88x9280 to 220xc2x0 C., preferably from 25 to 50xc2x0 C., and preferably in a hydrocarbon diluent or solvent, especially C4-12 aliphatic, cycloaliphatic or aromatic hydrocarbons or a mixture thereof.
Suitable addition polymerizable monomers for use with the foregoing novel catalyst compositions include ethylenically unsaturated monomers, acetylenic compounds, conjugated or non-conjugated dienes, and polyenes. Preferred monomers include olefins, for example alpha-olefins having from 2 to 20,000, preferably from 2 to 20, more preferably from 2 to 8 carbon atoms and combinations of two or more of such alpha-olefins. Particularly suitable alpha-olefins include, for example, ethylene, propylene, 1-butene, isobutylene, 1-pentene, 4-methylpentene-1,1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, or combinations thereof, as well as long chain vinyl terminated oligomeric or polymeric reaction products formed during the polymerization, and C10-30 xcex1-olefins specifically added to the reaction mixture in order to produce relatively long chain branches in the resulting polymers. Preferably, the alpha-olefins are ethylene, propylene, 1-butene, 1-pentene, 4-methyl-pentene-1,1-hexene, 1-octene, and combinations of ethylene and/or propene with one or more other alpha-olefins. Other preferred monomers include styrene, halo- or alkyl substituted styrenes, vinylbenzocyclobutene, 1,4-hexadiene, dicyclopentadiene, ethylidene norbomene, and 1,7-octadiene. Mixtures of the above-mentioned monomers may also be employed.
In general, the polymerization may be accomplished under conditions well known in the prior art for Ziegler-Natta or Kaminsky-Sinn type polymerization reactions. Suspension, solution, slurry, gas phase or high pressure, whether employed in batch or continuous form or other process conditions, may be employed if desired. Examples of such well known polymerization processes are depicted in U.S. Pat. Nos. 5,084,534, 5,405,922, 4,588,790, 5,032,652, 4,543,399, 4,564,647, 4,522,987, and elsewhere. Preferred polymerization temperatures are from 0-250xc2x0 C. Preferred polymerization pressures are from atmospheric to 3000 atmospheres (100 kPa to 300 Pma).
Preferred processing conditions include solution polymerization, more preferably continuous solution polymerization processes, conducted in the presence of an aliphatic or alicyclic liquid diluent. By the term xe2x80x9ccontinuous polymerizationxe2x80x9d is meant that at least the products of the polymerization are continuously removed from the reaction mixture. Preferably one or more reactants are also continuously added to the polymerization mixture during the polymerization. Examples of suitable aliphatic or alicyclic liquid diluents include straight and branched-chain C4-12 hydrocarbons and mixtures thereof; alicyclic hydrocarbons such as cyclohexane, cycloheptane, methylcyclohexane, methylcycloheptane, and mixtures thereof; and perfluorinated hydrocarbons such as perfluorinated C4-10 alkanes, and the like. Suitable diluents also include aromatic hydrocarbons (particularly for use with aromatic xcex1-olefins such as styrene or ring alkyl-substituted styrenes) including toluene, ethylbenzene or xylene, as well as liquid olefins (which may act as monomers or comonomers) including ethylene, propylene, 1-butene, isobutylene, butadiene, 1-pentene, cyclopentene, 1-hexene, cyclohexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1,4-hexadiene, 1-octene, 1-decene, styrene, divinylbenzene, allylbenzene, vinyltoluene (including all isomers alone or in admixture), and the like. Mixtures of the foregoing are also suitable. The foregoing diluents may also be advantageously employed during the synthesis of the metal complexes and catalyst activators of the present invention.
In most polymerization reactions the molar ratio of catalyst:polymerizable compounds employed is from 10xe2x88x9212:1 to 10xe2x88x921:1, more preferably from 10xe2x88x9212:1 to 10xe2x88x925:1.
Molecular weight control agents may be used in combination with the present cocatalysts. Examples of such molecular weight control agents include hydrogen, trialkyl aluminum compounds or other known chain transfer agents. A particular benefit of the use of the present cocatalysts is the ability (depending on reaction conditions) to produce narrow molecular weight distribution xcex1-olefin homopolymers and copolymers in greatly improved catalyst efficiencies. Preferred polymers have Mw/Mn of less than 2.5, more preferably less than 2.3. Such narrow molecular weight distribution polymer products are highly desirable due to improved tensile strength properties.
The catalyst composition of the present invention can also be employed to advantage in the gas phase polymerization and copolymerization of olefins, preferably by supporting the catalyst composition by any suitable technique. Gas phase processes for the polymerization of olefins, especially the homopolymerization and copolymerization of ethylene and propylene, and the copolymerization of ethylene with higher alpha olefins such as, for example, 1-butene, 1-hexene, 4-methyl-1-pentene are well known in the art. Such processes are used commercially on a large scale for the manufacture of high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE) and polypropylene.
The gas phase process employed can be, for example, of the type that employs a mechanically stirred bed or a gas fluidized bed as the polymerization reaction zone. Preferred is the process wherein the polymerization reaction is carried out in a vertical cylindrical polymerization reactor containing a fluidized bed of polymer particles supported above a perforated plate, the fluidization grid, by a flow of fluidization gas.
The gas employed to fluidize the bed comprises the monomer or monomers to be polymerized, and also serves as a heat exchange medium to remove the heat of reaction from the bed. The hot gases emerge from the top of the reactor, normally via a tranquilization zone, also known as a velocity reduction zone, having a wider diameter than the fluidized bed and wherein fine particles entrained in the gas stream have an opportunity to gravitate back into the bed. It can also be advantageous to use a cyclone to remove fine particles from the hot gas stream. The gas is then normally recycled to the bed by means of a blower or compressor and one or more heat exchangers to strip the gas of the heat of polymerization.
A preferred method of cooling of the bed, in addition to the cooling provided by the cooled recycle gas, is to feed a volatile liquid to the bed to provide an evaporative cooling effect. The volatile liquid employed in this case can be, for example, a volatile inert liquid, for example, a saturated hydrocarbon having about 3 to about 8, preferably 4 to 6, carbon atoms. In the case that the monomer or comonomer itself is a volatile liquid or can be condensed to provide such a liquid, this can be suitably be fed to the bed to provide an evaporative cooling effect. Examples of olefin monomers which can be employed in this manner are olefins containing from about 3 to about eight, preferably from 3 to six carbon atoms. The volatile liquid evaporates in the hot fluidized bed to form gas which mixes with the fluidizing gas. If the volatile liquid is a monomer or comonomer, it may undergo some polymerization in the bed. The evaporated liquid then emerges from the reactor as part of the hot recycle gas, and enters the compression/heat exchange part of the recycle loop. The recycle gas is cooled in the heat exchanger and, if the temperature to which the gas is cooled is below the dew point, liquid will precipitate from the gas. This liquid is desirably recycled continuously to the fluidized bed. It is possible to recycle the precipitated liquid to the bed as liquid droplets carried in the recycle gas stream, as described, for example, in EP-A-89691, U.S. Pat. No. 4,543,399, WO 94/25495 and U.S. Pat. No. 5,352,749. A particularly preferred method of recycling the liquid to the bed is to separate the liquid from the recycle gas stream and to reinject this liquid directly into the bed, preferably using a method that generates fine droplets of the liquid within the bed. This type of process is described in WO 94/28032.
The polymerization reaction occurring in the gas fluidized bed is catalyzed by the continuous or semi-continuous addition of catalyst. Such catalyst can be supported on an inorganic or organic support material if desired. The catalyst can also be subjected to a prepolymerization step, for example, by polymerizing a small quantity of olefin monomer in a liquid inert diluent, to provide a catalyst composite comprising catalyst particles embedded in olefin polymer particles.
The polymer is produced directly in the fluidized bed by catalyzed (co)polymerzation of the monomer(s) on the fluidized particles of catalyst, supported catalyst or prepolymer within the bed. Start-up of the polymerization reaction is achieved using a bed of preformed polymer particles, which, preferably, is similar to the target polyolefin, and conditioning the bed by drying with a dry inert gas such as nitrogen prior to introducing the catalyst, the monomer(s) and any other gases which it is desired to have in the recycle gas stream, such as a diluent gas, hydrogen chain transfer agent, or an inert condensable gas when operating in gas phase condensing mode. The produced polymer is discharged continuously or discontinuously from the fluidized bed as desired, optionally exposed to a catalyst kill and optionally pelletized.